1. Technical Field
The present application relates to light capturing sheets and light capturing rods that capture light by utilizing diffraction, and to light receiving devices using such light capturing sheets or light capturing rods, light emitting devices using such light capturing sheets or light capturing rods, and optical-fiber amplifiers using such light capturing sheets or light capturing rods.
2. Description of the Related Art
When causing light to propagate between two light propagation media having different refractive indices, since the light is transmitted and reflected at the interface, it is normally difficult to transfer the light from one light propagation medium to the other light propagation medium with high efficiency and to maintain this state. As a technique for capturing light from an ambient medium, such as air, into a transparent sheet, for example, a grating coupling technique in the related art discussed in “Hikari-Shuuseki-Kairo (Optical Integrated Circuit)” (Hiroshi Nishihara et al., Ohmsha Ltd., Feb. 25, 1985, p. 94, p. 243) is known. FIGS. 23A and 23B illustrate the principle of the grating coupling technique, and are a cross-sectional view and a plan view, respectively, of a light transmitting layer 20 provided with a linear grating having a pitch Λ at the surface thereof. As shown in FIG. 23A, when light 23a with a wavelength λ becomes incident on the grating at a specific incident angle θ, the light 23a becomes coupled to guided light 23B that propagates through the light transmitting layer 20.
“Hikari-Shuuseki-Kairo (Optical Integrated Circuit)” (Hiroshi Nishihara et al., Ohmsha Ltd., Feb. 25, 1985, p. 94, p. 243) is an example of the related art.